Atomic nature of the Schottky barrier height formation of the Ag/GaAs(001)-2 × 4 interface: An in-situ synchrotron radiation photoemission study

Abstract

The Interface of Ag with p-type α2 GaAs(001)-2×4 has been studied to further understand the formation mechanism of the Schottky barrier height (SBH). In the initial phase of Ag deposition, high-resolution core-level data show that Ag adatoms effectively passivate the surface As-As dimers without breaking them apart. The Ag(+)-As(−) dipoles are thus generated with a maximal potential energy of 0.26eV; a SBH of 0.38eV was measured. Greater Ag coverage causes elemental segregation of As/Ga atoms, reversing the direction of the net dipole. The band bending effect near the interface shows a downward shift of 0.08eV, and the final SBH is similar to the value as measured at the initial Ag deposition. Both parameters are secured at 0.25Å of Ag thickness prior to the observation of metallic behavior of Ag. Inadequacy of the metal-induced gap-state model for explaining SBH is evident.